1. Field of the Invention
The present invention generally relates to an apparatus for and a method of applying a surface treatment or coating on a large area masonry work, and more particularly to an apparatus for and method of applying an "exposed aggregate" surface.
2. Description of the Related Art
Commonly, skilled tradesmen finish concrete structures, such as, for example, paths, deckings, water features and swimming pools, with an exposed aggregate surface. The exposed aggregate surface typically comprises relatively small pebbles (i.e., aggregate) of a selected size bound together by a suitable cement binder.
Several different processes may be used to finish concrete structures with an exposed aggregate coating. One method involves application of a layer of epoxy adhesive cement to a cured concrete substrate and troweling the aggregate into the cement. Another method employs a seeding technique to apply a thin layer of aggregate to a concrete surface prior the cement hardening The seeded aggregate is worked into the cement to partially embed the aggregate. These processes, however, are labor intensive and require using skilled tradesmen Consequently, these methods are expensive and a small team of workers can only complete a small job in one day.
Other methods employ a washing step to remove excess cement. For example, one such method involves application of a portland cement and aggregate mixture to a cement substrate. The excess cement is washed away leaving the aggregate partially exposed A portland cement and aggregate mixture may also be sprayed onto a concrete substrate After spraying, localized pressure is applied over the surface of the mixture to pack the aggregate particles into the layer, and the excess portland cement is washed away. This method is disclosed in U.S. Pat. No. 4,198,472 issued to Brown, which is hereby incorporated by reference. The latter methods, however, have disadvantages when used on generally horizontal surfaces having a grade less than ten (10) percent. On horizontal surfaces, it is difficult to completely remove the cement slurry from the exposed aggregate layer Further, when applying an exposed aggregate coating to a structure such as a swimming pool, the water wash tends to puddle on the exposed aggregate surface at the bottom of the pool and must be removed by rags or absorbent rollers, such as paint rollers.